LSC

Design issues

Acoustics

Sustainable acoustics design of FE spaces, especially in urban areas, presents a number of acoustic challenges not least of which being the provision of suitably quiet teaching rooms in close proximity to noisy transport corridors. The following key acoustic challenges are tackled by this guide:

  • Spatial planning of an FE campus in a noisy area to mitigate noise levels falling on teaching / lecturing spaces and other acoustically sensitive spaces (this is primarily to facilitate natural ventilation of such spaces);
  • How to provide high sound insulation and natural ventilation / cooling (or low energy ventilation / cooling) to teaching/lecturing or other acoustically sensitive spaces that have to face noisy transport corridors or other sources of environmental noise; and
  • How to provide good acoustics environments inside low energy (low carbon) FE spaces whilst:
    • reducing the quantity of materials used; and
    • maximising the use of recycled materials.

Spatial Planning

Noise reduces with distance. Hence one approach to reducing the noise falling on sensitive components is to locate them as far as possible from noise sources. However, development sites are seldom large enough to enable this to make a material difference. Also locating teaching / lecturing space in this way reduces development density and would constrain external education / circulation / recreation space to the area between teaching spaces and the noise source(s). This area would therefore be very noisy, limiting its value to the FE facility.

There are two principal methods for reducing noise across the site – to the benefit of internal education spaces and external education / circulation / recreation space.

Option #1: Noise Barrier / Bund

The first option is to construct a noise barrier at the site boundary with the noise source. The screen could be provided by either an earthen bund (or landscaped feature), a noise barrier (fence) or a mix of both.

Figure 1 shows that the college can be built taller if it is developed further back from the barrier or if the barrier itself is made taller.

An earthen structure can be made into a landscaped public realm feature.

There are however a number of challenges with this approach:

  • To be effective the barrier will have to cover the length of the site
  • The barrier may be costly (unless it could be constructed from materials extracted elsewhere on the site which would otherwise have to be disposed of);
  • If the noise source is a road then there is no ‘active frontage’ to the road which may be considered unacceptable to the planning authority and also to the FE.
  • It suggests a new ‘gated development’.

 

    Figure 1


      Option #2: Site Planning

      The alternative option is to develop less noise sensitive elements of the college development (e.g. students union, labs, sports facilities or mechanically ventilated spaces, e.g. music, drama, large lecture theatre etc) adjacent to the boundary of the road / railway or other noise source. This ‘front line development’ then forms a noise screen for the rest of the site. An example is presented in Figure 2

      Figure 2: Example Noise Maps showing screening effect of buildings adjacent to a main road


      Figure 2

      This approach maximises development density, reduces the noise at teaching /lecturing spaces such that they can be naturally ventilated, reduces noise at outdoor circulation/teaching/recreation space and can provide an active frontage.

      High Sound Insulation and Natural Ventilation

      With good design (for example, to facades and ventilation systems), sustainable teaching and lecturing spaces with good internal environments can be achieved in the ‘edge developments’.

      A key issue is noise break-in through the building facades. The obvious solution would be to construct heavy facades and use mechanical ventilation. However, low carbon solutions are possible.

      Figure 3 provides an example of using a ‘twin skin’ façade that provides both noise insulation but also supports natural ventilation.


      Figure 3


      Figure 4: Ventilation Passive Natural

      Figure 4

      Figure 4 shows an example of using acoustically treated inlet vents in the facades to allow fresh air into the teaching spaces. Proprietary acoustic vents can be used, or increased ventilation open area can be achieved using labyrinthine routing with sound absorbent lining. In order to reduce the level of noise entering the building, ventilation inlets should be positioned on quieter sides of the building.

      The fresh air exits via passive stacks high at the rear of the room into a central duct and up to the roof outlet.

      Reduced Materials and Recycled Materials

      The acoustic environment in an education space is known to be important to learning. BB93 provides mandatory comprehensive acoustic guidance for primary and secondary education spaces. BB93 is not mandatory for FE spaces, but it does provide a critical basis for the design of successful spaces.

      Whilst BB93 should guide the design where ever reasonably practicable, it has been demonstrated that successful learning in the healthy adult population is less reliant on a very good acoustic environment. Hence very successful FE spaces can be delivered using a relaxed version of BB93 in a number of targeted and carefully considered areas.

      For example, allowing a slightly higher ambient noise level in some rooms can enable a larger proportion of teaching spaces to be naturally ventilated. This gives less reliance on mechanical ventilation, which reduces capital cost and energy use. A relaxation of target reverberation time in appropriate rooms can reduce the total area of sound absorbing finishes, which reduces capital cost, resource usage and embodied energy usage.